Nope, they will not work with wod models. But you don't need to download another client, simply follow these steps
1.) Goto WoW directory, open Data folder, delete "patch-w.mpq"
2.) Open enUS file inside Data folder, delete "patch-enUS-w.mpq"
3.) Put Patch A and patch B (for char models) into Data folder
If u don't want to mess with your existing client, make a copy of the entire wow folder and use one of the wow folder for installing these models

@Helzing Yeah characters are quite flawless, if u find something strange, you can report it here (I will report it in Modcraft)

I've been leveling my Hunter using these new models and I encountered many NPC that cause a client crash upon taking or turning a quest in. (One of them being the Stable master in Dolanaar). I suspect there might be many other buggy NPCs of that sort.